Thin film forming material, thin film, and method for manufacturing thin film

Abstract

To provide a raw material for forming a high-quality thin film containing a sodium compound with good steamability.SOLUTION: The present invention provides a raw material for forming a thin film that contains at least one sodium compound represented by general formula (1), a thin film and a method for producing a thin film (where R1 is a C4 to 10 branched alkyl group (excluding tert-butyl groups) or a C3 to 10 branched alkyl group with one or more hydrogen atoms substituted with C1 to 5 alkoxy groups).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a thin film-forming raw material containing a sodium compound, a thin film obtained by using the thin film-forming raw material, and a method for producing the thin film.

[0002] Lithium-ion secondary batteries are small, lightweight, have high energy density, high capacity, and can be repeatedly charged and discharged. As a result, they are being increasingly used in portable electronic devices such as smartphones, portable personal computers, and handheld video cameras, as well as in electric vehicles, hybrid vehicles that use electricity as part of their power source, and as storage batteries as a core technology for the spread of natural energy, and demand for them is steadily expanding.

[0003] A battery is composed of a combination of a positive electrode, a negative electrode, and an electrolyte. The positive and negative electrodes determine the battery's energy, and the electrolyte functions as a conductive path for metal ions. Lithium-ion secondary batteries use an organic solvent as the electrolyte, but because the electrolyte is a flammable organic solvent, they have issues such as leakage and fire. All-solid-state batteries, which have a solid electrolyte, are expected to solve these issues and improve safety. Furthermore, it has been pointed out that all-solid-state batteries may be able to produce batteries with higher performance (large capacity, high output, etc.) than lithium-ion secondary batteries, and they are expected to be a powerful secondary battery device that will lead to the expansion of electric vehicles and smart grids.

[0004] The electrolyte of an all-solid-state battery is required to be able to cover the complex unevenness of the battery substrate and electrodes such as the positive and negative electrodes. As a method for covering the battery substrate and electrodes, a method of coating the battery substrate and electrodes with a thin film containing metal atoms has been investigated.

[0005] Methods for manufacturing thin films include sputtering, ion plating, metal organic decomposition (MOD) methods such as coating pyrolysis and sol-gel methods, chemical vapor deposition (CVD), and atomic layer deposition (ALD), which is a type of CVD method. Of these, CVD and ALD are primarily used because of the good quality of the thin films they produce.

[0006] CVD and ALD are thin film deposition techniques using chemical vapor deposition. ALD in particular is expected to be a thin film deposition technique that can form thin films with fine shapes, as it can grow materials supplied by precursors onto substrate surfaces of various compositions and control the atomic layer of the thin film surface.

[0007] For example, Patent Document 1 discloses an apparatus for forming a solid electrolyte membrane using an organic lithium compound as a raw material, and describes dipivaloylmetalithium (CAS number: 22441-13-0), lithium tert-butoxide (CAS number: 1907-33-1), and lithium trimethylsilylamide (CAS number: 4039-32-1) as the organic lithium compound. Furthermore, Patent Document 2 discloses the formation of a lithium-containing thin film using a lithium precursor such as lithium tert-butoxide by the ALD method. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2020-004592 [Patent Document 2] Special Publication No. 2011-508826 Summary of the Invention [Problem to be solved by the invention]

[0009] However, lithium is a rare metal, and only a limited number of countries produce it. In recent years, concerns have arisen about rising raw material prices due to tight supply and demand. Therefore, there is a need to develop materials that can replace lithium. Sodium, an alkali metal with similar properties to lithium, is attracting attention. It is also readily available and inexpensive in Japan. However, while sodium tert-butoxide, for example, vaporizes at low temperatures, when used as a thin-film forming material, it leaves a large amount of residual impurities (residual carbon) in the thin film, and the quality of the thin films formed using sodium tert-butoxide is not satisfactory.

[0010] Therefore, an object of the present invention is to provide a thin film-forming material that contains a sodium compound and is capable of forming a high-quality thin film. [Means for solving the problem]

[0011] As a result of extensive research, the present inventors have found that a thin film-forming raw material containing a sodium compound having a specific structure can solve the above problems, and have thus completed the present invention. That is, the present invention provides the following inventions [1] to

[10] .

[0012] [1] A thin film-forming material containing at least one sodium compound represented by the following general formula (1):

[0013] [ka]

[0014] (In the formula, R 1 represents a branched alkyl group having 4 to 10 carbon atoms (excluding tert-butyl group) or a branched alkyl group having 3 to 10 carbon atoms in which one or more hydrogen atoms are substituted with an alkoxy group having 1 to 5 carbon atoms.

[0015] [2] R in the general formula (1) 1is a secondary alkyl group having 4 to 10 carbon atoms, a tertiary alkyl group having 5 to 10 carbon atoms, or a branched alkyl group having 3 to 10 carbon atoms in which one or more hydrogen atoms are substituted with an alkoxy group having 1 to 5 carbon atoms.

[0016] [3] The thin film-forming material according to [1] or [2], wherein the sodium compound is a compound represented by the following general formula (2):

[0017] [ka]

[0018] (In formula (2), R 2 represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and R 3 and R 4 each independently represents an alkyl group having 1 to 5 carbon atoms, and R 2 , R 3 and R 4 The total number of carbon atoms in the alkyl group represented by the formula (I) is 8 or less.

[0019] [4] A thin film obtained by using the thin film-forming material according to any one of [1] to [3].

[0020] [5] A method for producing a thin film, comprising forming a thin film containing sodium atoms using the thin film-forming material according to any one of [1] to [3].

[0021] [6] The method for producing a thin film according to [5], comprising: a source gas introduction step of introducing a source gas obtained by vaporizing the thin film-forming source material into a film formation chamber in which a substrate is placed; and a thin film formation step of decomposing and / or chemically reacting the sodium compound represented by general formula (1) contained in the source gas to form a thin film containing sodium atoms on the surface of the substrate.

[0022] [7] The method for producing a thin film according to [6], further comprising a precursor thin film formation step, between the source gas introduction step and the thin film formation step, of depositing a compound represented by general formula (1) contained in the source gas on the surface of the substrate to form a precursor thin film, wherein the thin film formation step is a step of reacting the precursor thin film with a reactive gas to form a thin film containing sodium atoms on the surface of the substrate.

[0023] [8] The method for producing a thin film according to [7], wherein the reactive gas is an oxidizing gas and the thin film is sodium oxide.

[0024] [9] The method for producing a thin film according to [8], wherein the oxidizing gas is a gas containing oxygen, ozone, or water vapor.

[0025]

[10] The method for producing a thin film according to any one of [7] to [9], wherein the thin film forming step comprises reacting the precursor thin film with the reactive gas at a temperature in the range of 100°C to 400°C. [Effects of the Invention]

[0026] According to the present invention, it is possible to provide a thin film-forming raw material that contains a sodium compound having good vapor properties and that is capable of forming a smooth, high-quality thin film with little residual carbon. Furthermore, by using the thin film-forming raw material of the present invention, it is possible to provide a smooth, high-quality thin film with little residual carbon and a method for producing a thin film. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a schematic diagram showing an example of an ALD apparatus used in the thin film manufacturing method according to the present invention. [Figure 2] FIG. 1 is a schematic diagram showing another example of an ALD apparatus used in the thin film manufacturing method according to the present invention. [Figure 3] FIG. 1 is a schematic diagram showing yet another example of an ALD apparatus used in the thin film manufacturing method according to the present invention. [Figure 4] FIG. 1 is a schematic diagram showing yet another example of an ALD apparatus used in the thin film manufacturing method according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0028] A. Raw materials for thin film formation A1. Sodium compound represented by general formula (1) The thin film-forming material of the present invention contains at least one sodium compound represented by the above general formula (1).

[0029] In the above general formula (1), R 1 represents a branched alkyl group having 4 to 10 carbon atoms, excluding a tert-butyl group, or a branched alkyl group having 3 to 10 carbon atoms in which one or more hydrogen atoms are substituted with an alkoxy group having 1 to 5 carbon atoms.

[0030] In this specification, the number of carbon atoms in a group refers to the number of carbon atoms in the group after substitution of a hydrogen atom with a substituent. For example, when a hydrogen atom in an alkyl group having 4 to 10 carbon atoms is substituted, 4 to 10 carbon atoms refers to the number of carbon atoms after the hydrogen atom is substituted. Furthermore, the number of carbon atoms in a branched alkyl group in which one or more hydrogen atoms are substituted with an alkoxy group having 1 to 5 carbon atoms refers to the number of carbon atoms in the branched alkyl group after substitution with an alkoxy group having 1 to 5 carbon atoms.

[0031] In the present invention, when used as a thin film forming material, it is possible to form a thin film with little residual carbon. 1 However, it is preferably a secondary alkyl group having 4 to 10 carbon atoms, a tertiary alkyl group having 5 to 10 carbon atoms, or a branched alkyl group having 3 to 10 carbon atoms in which one or two or more hydrogen atoms have been substituted with an alkoxy group having 1 to 5 carbon atoms, and more preferably a branched alkyl group having 3 to 10 carbon atoms in which one or two or more hydrogen atoms have been substituted with an alkoxy group having 1 to 5 carbon atoms.

[0032] Above R 1However, when the secondary alkyl group has 4 to 10 carbon atoms, it is possible to form a thin film with little residual carbon, so that the secondary alkyl group is preferably a secondary alkyl group having 4 to 9 carbon atoms, more preferably a secondary alkyl group having 5 to 8 carbon atoms, even more preferably a secondary alkyl group having 6 or 7 carbon atoms, and most preferably a 2,4-dimethyl-3-pentyl group. Specific examples of the secondary alkyl group having 4 to 10 carbon atoms include a propan-2-yl group, a butan-2-yl group, a sec-butyl group, a 3-methyl-2-butyl group, a 2-methyl-3-pentyl group, a 2,4-dimethyl-3-pentyl group, a 2,2-dimethyl-3-hexyl group, and a 2,2,4,4-tetramethyl-3-pentyl group.

[0033] Above R 1 However, when the tertiary alkyl group has 5 to 10 carbon atoms, it is possible to form a thin film with little residual carbon, so the tertiary alkyl group is preferably a tertiary alkyl group having 6 to 10 carbon atoms, more preferably a tertiary alkyl group having 7 to 9 carbon atoms, and most preferably a 2,4,4-trimethyl-2-pentyl group. Specific examples of the tertiary alkyl group having 5 to 10 carbon atoms include, for example, a 2-methyl-2-butyl group, a 2-methyl-2-pentyl group, a 2-ethyl-2-pentyl group, a 3-methyl-3-pentyl group, a 3-ethyl-3-pentyl group, a 2-methyl-2-hexyl group, a 3-methyl-3-hexyl group, a 3-ethyl-3-hexyl group, a 3-ethyl-2-methyl-3-hexyl group, a 4-ethyl-4-heptyl group, a 2, Examples include a 3,3-trimethyl-2-butyl group, a 2,4,4-trimethyl-2-pentyl group, a 2-methyl-2-octyl group, a 2-ethyl-2-octyl group, a 3-methyl-3-octyl group, a 3-ethyl-3-octyl group, a 4-methyl-4-octyl group, a 4-ethyl-octyl group, a 2-methyl-2-nonyl group, a 3-methyl-3-nonyl group, a 4-methyl-4-nonyl group, and a 5-methyl-5-nonyl group.

[0034] Above R 1However, when the branched-chain alkyl group is a branched-chain alkyl group having 3 to 10 carbon atoms in which one or more hydrogen atoms have been substituted with an alkoxy group having 1 to 5 carbon atoms, a thin film with little residual carbon can be formed. Therefore, the branched-chain alkyl group is preferably a branched-chain alkyl group having 5 to 9 carbon atoms substituted with an alkoxy group having 1 to 3 carbon atoms, more preferably a branched-chain alkyl group having 6 to 8 carbon atoms substituted with an alkoxy group having 1 to 3 carbon atoms, and most preferably a 2-methyl-1-propoxy-2-propyl group. Specific examples of the branched alkyl group having 3 to 10 carbon atoms in which one or more hydrogen atoms are substituted by an alkoxy group having 1 to 5 carbon atoms include a 1-methoxy-2-methyl-2-propyl group, a 1-ethoxy-2-methyl-2-propyl group, a 2-methyl-1-propoxy-2-propyl group, a 1-methoxy-2-methyl-2-butyl group, a 3-(methoxymethyl)-3-pentyl group, and a 3-methoxy-2,3-dimethyl-2-butyl group.

[0035] R 1 is a branched alkyl group having 4 to 10 carbon atoms in which one or more hydrogen atoms are substituted with an alkoxy group having 1 to 5 carbon atoms, a thin film with little residual carbon can be formed. 1 is preferably a group represented by the following general formula (2'): That is, the sodium compound is preferably a compound represented by the following general formula (2).

[0036] [ka]

[0037] In general formula (2'), R 2 represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and R 3 and R 4 each independently represents an alkyl group having 1 to 5 carbon atoms, * represents the position at which the alkyl group is bonded to the oxygen atom of the sodium compound represented by formula (1), and R 2 , R 3 and R 4The total number of carbon atoms in the alkyl group represented by the formula (I) is 8 or less.

[0038] [ka]

[0039] In general formula (2), R 2 represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and R 3 and R 4 each independently represents an alkyl group having 1 to 5 carbon atoms, and R 2 , R 3 and R 4 The total number of carbon atoms in the alkyl group represented by the formula (I) is 8 or less.

[0040] R 2 , R 3 and R 4 Examples of the alkyl group having 1 to 5 carbon atoms represented by the formula (I) include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, and a pentyl group.

[0041] The thin film forming material of the present invention can form a thin film with little residual carbon, so R 2 or R 4 However, it is preferably an alkyl group having 1 to 3 carbon atoms, and more preferably a methyl group. Furthermore, the thin film forming material of the present invention can form a thin film with little residual carbon, so R 2 and R 4 and both are preferably alkyl groups having 1 to 3 carbon atoms, and more preferably methyl groups.

[0042] The thin film forming material of the present invention can form a thin film with little residual carbon. 3 is preferably an alkyl group having 1 to 3 carbon atoms, more preferably a linear alkyl group having 1 to 3 carbon atoms, and most preferably an n-propyl group.

[0043] Preferred specific examples of the sodium compound represented by the general formula (1) include the following compounds No. 1 to No. 65, but the present invention is not limited to these compounds. In the following compounds No. 1 to No. 65, "Me" represents a methyl group, "Et" represents an ethyl group, "nPr" represents an n-propyl group, "iPr" represents an isopropyl group, and "tBu" represents a tert-butyl group.

[0044] [ka]

[0045] [ka]

[0046] [ka]

[0047] [ka]

[0048] [ka]

[0049] [ka]

[0050] [ka]

[0051] [ka]

[0052] [ka]

[0053] [ka]

[0054] [ka]

[0055] [ka]

[0056] [ka]

[0057] The sodium compound represented by the general formula (1) can be produced by a known method. For example, 1 However, the sodium compound having a 2,4-dimethyl-3-pentyl group can be produced by reacting sodium amide with 2,4-dimethyl-3-pentanol in the presence of a solvent such as toluene, and then removing the solvent.

[0058] In order to ensure transportability in the piping of a film-forming apparatus used when producing a thin film using the thin-film-forming material of the present invention, the sodium compound represented by the general formula (1) preferably has a melting point of less than 150°C, and more preferably is liquid at room temperature.

[0059] A2.Other precursors The thin film-forming raw material of the present invention may contain the sodium compound represented by the above general formula (1), and the composition thereof varies depending on the type of the target thin film. For example, when producing a thin film containing only sodium atoms as metal, the thin film-forming raw material of the present invention does not contain any metal compounds or semimetal compounds other than sodium atoms. On the other hand, when producing a thin film containing sodium atoms and metals and / or metalloids other than sodium atoms, the thin film-forming raw material of the present invention can contain, in addition to the sodium compound represented by general formula (1), a compound containing the desired metal and / or a compound containing a metalloid (hereinafter referred to as "other precursors").

[0060] The other precursors used together with the sodium compound represented by the general formula (1) above are not particularly limited, and any well-known precursors used in thin film forming materials can be used. Examples of the other precursor include compounds of silicon or a metal with one or more compounds selected from the group consisting of compounds used as organic ligands, such as alcohol compounds, glycol compounds, β-diketone compounds, cyclopentadiene compounds, and organic amine compounds. Examples of the metal species of the precursor include lithium, sodium, magnesium, aluminum, potassium, calcium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, rubidium, strontium, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, indium, tin, antimony, barium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, lead, bismuth, radium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium.

[0061] Examples of alcohol compounds that can be used as organic ligands for the other precursors include alkyl alcohols such as methanol, ethanol, propanol, isopropyl alcohol, butanol, sec-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, pentyl alcohol, isopentyl alcohol, and tert-pentyl alcohol; 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, 2-(2-methoxyethoxy)ethanol, 2-methoxy-1-methylethanol, 2-methoxy-1,1-dimethylethanol, 2-ethoxy-1,1-dimethylethanol, and 2-isopropoxy-1,1-dimethylethanol. ether alcohols such as 2-butoxy-1,1-dimethylethanol, 2-(2-methoxyethoxy)-1,1-dimethylethanol, 2-propoxy-1,1-diethylethanol, 2-sec-butoxy-1,1-diethylethanol, and 3-methoxy-1,1-dimethylpropanol; and dialkylamino alcohols such as dimethylaminoethanol, ethylmethylaminoethanol, diethylaminoethanol, dimethylamino-2-pentanol, ethylmethylamino-2-pentanol, dimethylamino-2-methyl-2-pentanol, ethylmethylamino-2-methyl-2-pentanol, and diethylamino-2-methyl-2-pentanol.

[0062] Examples of glycol compounds used as organic ligands for the other precursors include 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 2,4-hexanediol, 2,2-dimethyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 1,3-butanediol, 2,4-butanediol, 2,2-diethyl-1,3-butanediol, 2-ethyl-2-butyl-1,3-propanediol, 2,4-pentanediol, 2-methyl-1,3-propanediol, 2-methyl-2,4-pentanediol, 2,4-hexanediol, and 2,4-dimethyl-2,4-pentanediol.

[0063] Examples of the β-diketone compound used as the organic ligand for the other precursors include acetylacetone, hexane-2,4-dione, 5-methylhexane-2,4-dione, heptane-2,4-dione, 2-methylheptane-3,5-dione, 5-methylheptane-2,4-dione, 6-methylheptane-2,4-dione, 2,2-dimethylheptane-3,5-dione, 2,6-dimethylheptane-3,5-dione, 2,2,6-trimethylheptane-3,5-dione, 2,2,6,6-tetramethylheptane-3,5-dione, octane-2,4-dione, 2,2,6-trimethyloctane-3,5-dione, 2,6-dimethyloctane-3,5-dione, 2,9-dimethylnonane-4,6-dione, 2-methyl- Examples of suitable fluorine-substituted alkyl β-diketones include 6-ethyldecane-3,5-dione and 2,2-dimethyl-6-ethyldecane-3,5-dione; 1,1,1-trifluoropentane-2,4-dione, 1,1,1-trifluoro-5,5-dimethylhexane-2,4-dione, 1,1,1,5,5,5-hexafluoropentane-2,4-dione and 1,3-diperfluorohexylpropane-1,3-dione; and ether-substituted β-diketones include 1,1,5,5-tetramethyl-1-methoxyhexane-2,4-dione, 2,2,6,6-tetramethyl-1-methoxyheptane-3,5-dione and 2,2,6,6-tetramethyl-1-(2-methoxyethoxy)heptane-3,5-dione.

[0064] Examples of cyclopentadiene compounds used as organic ligands for the other precursors include cyclopentadiene, methylcyclopentadiene, ethylcyclopentadiene, propylcyclopentadiene, isopropylcyclopentadiene, butylcyclopentadiene, sec-butylcyclopentadiene, isobutylcyclopentadiene, tert-butylcyclopentadiene, dimethylcyclopentadiene, and tetramethylcyclopentadiene. Examples of organic amine compounds used as organic ligands include methylamine, ethylamine, propylamine, isopropylamine, butylamine, sec-butylamine, tert-butylamine, isobutylamine, dimethylamine, diethylamine, dipropylamine, diisopropylamine, ethylmethylamine, propylmethylamine, and isopropylmethylamine.

[0065] The other precursors mentioned above are known in the art, and their production methods are also known. For example, when an alcohol compound is used as the organic ligand, the precursor can be produced by reacting the inorganic salt of the metal or a hydrate thereof described above with an alkali metal alkoxide of the alcohol compound. Here, examples of the inorganic salt of the metal or a hydrate thereof include metal halides and nitrates, and examples of the alkali metal alkoxide include sodium alkoxide, lithium alkoxide, and potassium alkoxide.

[0066] When the method for transporting and supplying a thin film-forming raw material of the present invention is a single-source method described below, the other precursor is preferably a compound whose thermal and / or oxidative decomposition behavior is similar to that of the sodium compound represented by the general formula (1).When the method for transporting and supplying a thin film-forming raw material is a cocktail-source method described below, the other precursor is preferably a compound whose thermal and / or oxidative decomposition behavior is similar to that of the sodium compound represented by the general formula (1) and which does not undergo deterioration due to chemical reactions or the like when mixed.

[0067] A3. Organic solvents The thin film-forming material of the present invention contains the sodium compound, and may contain an organic solvent, if necessary. The organic solvent is not particularly limited, and any well-known organic solvent can be used. Examples of the organic solvent include acetates such as ethyl acetate, butyl acetate, and methoxyethyl acetate; ethers such as tetrahydrofuran, tetrahydropyran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, dibutyl ether, and dioxane; ketones such as methyl butyl ketone, methyl isobutyl ketone, ethyl butyl ketone, dipropyl ketone, diisobutyl ketone, methyl amyl ketone, cyclohexanone, and methylcyclohexanone; hydrocarbons such as hexane, cyclohexane, methylcyclohexane, dimethylcyclohexane, ethylcyclohexane, heptane, octane, toluene, and xylene; hydrocarbons having a cyano group such as 1-cyanopropane, 1-cyanonobutane, 1-cyanohexane, cyanocyclohexane, cyanobenzene, 1,3-dicyanopropane, 1,4-dicyanobutane, 1,6-dicyanohexane, 1,4-dicyanocyclohexane, and 1,4-dicyanobenzene; pyridine, lutidine, and the like. These organic solvents may be used alone or in combination of two or more depending on the solubility of the solute, the relationship between the temperature used and the boiling point, the flash point, and the like.

[0068] When the thin film manufacturing method of the present invention uses the cocktail source method described below, it is preferable that the thin film forming raw material contains an organic solvent, since this facilitates uniform supply of the sodium compound represented by the general formula (1) and other precursors.

[0069] When the thin film-forming raw material of the present invention is a mixed solution with the above-mentioned organic solvent, from the viewpoint of being able to produce a thin film with good productivity, the total amount of precursors in the thin film-forming raw material is preferably 0.01 mol / L to 2.0 mol / L, and more preferably 0.05 mol / L to 1.0 mol / L.

[0070] Here, the total amount of precursors means the amount of the sodium compound represented by the general formula (1) when the thin film-forming raw material of the present invention does not contain any other precursors other than the sodium compound represented by the general formula (1) above, and means the total amount of the sodium compound represented by the general formula (1) above and the other precursors when the thin film-forming raw material of the present invention contains other precursors in addition to the sodium compound represented by the general formula (1) above.

[0071] A4. Nucleophilic reagents Furthermore, the thin-film-forming raw material of the present invention may contain a nucleophilic reagent, if necessary, to improve the stability of the sodium compound represented by the general formula (1) and other precursors. Examples of the nucleophilic reagent include ethylene glycol ethers such as glyme, diglyme, triglyme, and tetraglyme; crown ethers such as 18-crown-6, dicyclohexyl-18-crown-6, 24-crown-8, dicyclohexyl-24-crown-8, and dibenzo-24-crown-8; ethylenediamine, N,N'-tetramethylethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, 1,1,4,7,7-pentamethyldiethylenetriamine, and 1,1,4,7,10,10-hexamethyltriethylenetetramine; Examples of suitable nucleophilic reagents include polyamines such as triethoxytriethyleneamine, cyclic polyamines such as cyclam and cyclen, heterocyclic compounds such as pyridine, pyrrolidine, piperidine, morpholine, N-methylpyrrolidine, N-methylpiperidine, N-methylmorpholine, tetrahydrofuran, tetrahydropyran, 1,4-dioxane, oxazole, thiazole, and oxathiolane, β-ketoesters such as methyl acetoacetate, ethyl acetoacetate, and 2-methoxyethyl acetoacetate, and β-diketones such as acetylacetone, 2,4-hexanedione, 2,4-heptanedione, 3,5-heptanedione, and dipivaloylmethane. The amount of these nucleophilic reagents used is preferably 0.1 to 10 moles, more preferably 1 to 4 moles, per mole of the total precursor.

[0072] A5. Impurities It is desirable that the thin film-forming raw material of the present invention contains as little impurity metal elements, impurity halogens such as impurity chlorine, and impurity organic components as possible, except for the above-mentioned constituent components, i.e., the sodium compound represented by the general formula (1), the other precursors, the organic solvent, the nucleophilic reagent, and the like that constitute the thin film-forming raw material. The impurity metal element content is preferably 100 ppb or less, more preferably 10 ppb or less, for each element, and preferably 1 ppm or less, more preferably 100 ppb or less in total. In particular, when used as a gate insulating film, gate film, or barrier layer of an LSI, it is necessary to reduce the content of alkali metal elements and alkaline earth metal elements, which affect the electrical properties of the resulting thin film. The impurity halogen content is preferably 100 ppm or less, more preferably 10 ppm or less, and even more preferably 1 ppm or less.The total amount of impurity organic content is preferably 500 ppm or less, more preferably 50 ppm or less, and even more preferably 10 ppm or less. Furthermore, since moisture can cause particle generation in the thin film-forming raw material of the present invention and during thin film formation, it is advisable to remove as much moisture as possible from the sodium compound represented by general formula (1), other precursors, organic solvents, and nucleophilic reagents before use in order to reduce their respective moisture contents. The moisture content of each of the sodium compound represented by general formula (1), other precursors, organic solvents, and nucleophilic reagents is preferably 10 ppm or less, more preferably 1 ppm or less.

[0073] Furthermore, in order to reduce or prevent particle contamination of the thin film to be formed, it is preferable that the thin film-forming raw material of the present invention contains as few particles as possible. Specifically, in particle measurement in the liquid phase using a light scattering liquid-borne particle detector, the number of particles larger than 0.3 μm is preferably 100 or less per 1 ml of liquid phase, and the number of particles larger than 0.2 μm is more preferably 100 or less per 1 ml of liquid phase.

[0074] A6. Uses of raw materials for thin film formation The physical properties of the sodium compound represented by the general formula (1) are suitable for the CVD method, and therefore the thin film-forming raw material of the present invention is useful as a chemical vapor deposition raw material (hereinafter, also referred to as a "CVD raw material"). In particular, the sodium compound represented by the general formula (1) has a wide ALD window, and therefore the thin film-forming raw material of the present invention is particularly suitable for the ALD method. Therefore, the thin film-forming raw material of the present invention is particularly useful as a thin film-forming raw material for the ALD method.

[0075] B. Thin Film Manufacturing Methods Next, a method for producing a thin film using the thin film-forming material of the present invention will be described. The method for producing a thin film of the present invention is not particularly limited as long as it includes forming a thin film containing sodium atoms using the above-mentioned thin film-forming raw material. For example, it is preferable that the method includes a raw material gas introduction step of introducing a raw material gas obtained by vaporizing the above-mentioned thin film-forming raw material into a film formation chamber in which a substrate is placed, and a thin film formation step of decomposing and / or chemically reacting the sodium compound represented by general formula (1) contained in the raw material gas to form a thin film containing sodium atoms on the surface of the substrate. Among these, it is more preferable to produce a thin film by the ALD method, which easily produces a high-quality thin film with little residual carbon, and which includes, between the source gas introduction step and the thin film formation step, a precursor thin film formation step of forming a precursor thin film on the surface of the substrate using the thin film-forming raw material, and the thin film formation step includes a step of reacting the precursor thin film with a reactive gas to form a thin film containing sodium atoms on the surface of the substrate.

[0076] There are no particular limitations on the method of transporting and supplying raw materials, the deposition method, the manufacturing conditions, the manufacturing equipment, etc., and well-known general conditions and methods can be used.

[0077] A well-known ALD apparatus can be used as an apparatus for producing a thin film using the thin film-forming raw material of the present invention. Specific examples of such an apparatus include an apparatus capable of supplying a precursor by bubbling, as shown in FIGS. 1 and 3, and an apparatus having a vaporization chamber, as shown in FIGS. 2 and 4. Another example is an apparatus capable of performing plasma treatment on a reactive gas, as shown in FIGS. 3 and 4. It should be noted that the apparatus is not limited to the single-wafer apparatus equipped with a film-forming chamber (deposition reaction section) as shown in FIGS. 1 to 4, but an apparatus capable of simultaneously processing multiple wafers using a batch furnace can also be used. These can also be used as CVD apparatus.

[0078] Each step in the method for producing such a thin film will be described below.

[0079] B1. Raw material gas introduction process The source gas introduction step in the present invention is a step of introducing a source gas obtained by vaporizing a thin film forming source material into a film formation chamber in which a substrate is placed. Methods for introducing the source gas obtained by vaporizing the above-mentioned thin film-forming raw material into a film-forming chamber in which a substrate is placed include a gas transport method, a liquid transport method, a single source method, a cocktail source method, and the like.

[0080] As an example of the gas transport method, as shown in Figures 1 and 3, a method in which the thin film forming raw material of the present invention is heated and / or vaporized in a container (hereinafter, sometimes referred to as a "raw material container") in which the thin film forming raw material of the present invention is stored to form a raw material gas, and the raw material gas is introduced into a film formation chamber in which a substrate is placed, together with a carrier gas such as argon, nitrogen, or helium as necessary. As an example of the liquid transport method, as shown in Figures 2 and 4, a method in which a thin film forming raw material is transported in a liquid or solution state to a vaporization chamber, heated and / or vaporized in the vaporization chamber to form a raw material gas, and the raw material gas is introduced into a film formation chamber. In the gas transport method, the sodium compound represented by the general formula (1) itself can be used as the thin film-forming raw material. In the liquid transport method, the sodium compound represented by the general formula (1) itself or a solution of the sodium compound in the organic solvent can be used as the thin film-forming raw material. In the gas transport method and the liquid transport method, the thin film-forming raw material may contain the other precursors, the nucleophilic reagent, etc.

[0081] The single source method is a method for transporting and supplying a thin film forming material containing precursors of multiple components, and includes a method in which each precursor is vaporized and supplied independently. The cocktail source method includes, for example, vaporizing and supplying a mixed raw material in which multi-component precursors are mixed in advance in a desired composition. The thin film-forming raw material containing these multi-component precursors may also contain the above-mentioned nucleophilic reagent.

[0082] The step of vaporizing the thin film-forming raw material of the present invention to obtain a raw material gas may be carried out in a raw material container as described above, or in a vaporization chamber. In either case, the thin film-forming raw material of the present invention is preferably vaporized at 0°C to 200°C, as this facilitates the formation of a high-quality thin film. Furthermore, when the thin film forming raw material is vaporized in the raw material container or vaporization chamber to produce the raw material gas, the pressure in the raw material container and the vaporization chamber is preferably within the range of 1 Pa to 10,000 Pa, since the thin film forming raw material is easily vaporized.

[0083] Examples of materials for the substrate placed in the film formation chamber include silicon; ceramics such as silicon dioxide, silicon nitride, titanium nitride, tantalum nitride, titanium oxide, ruthenium oxide, zirconium oxide, hafnium oxide, and lanthanum oxide; glass; and metals such as metallic cobalt and metallic ruthenium. The substrate may have a plate-like, spherical, fibrous, or flake-like shape. The substrate surface may be flat or may have a three-dimensional structure such as a trench structure.

[0084] B2. Thin film formation process The thin film forming step is a step of forming a thin film containing sodium atoms on the surface of the substrate by decomposing and / or chemically reacting the sodium compound represented by general formula (1) contained in the source gas. As shown in Figures 1 to 4, the thin film formation process is a process carried out in a film formation chamber in which a substrate is placed, in which a raw material gas and a reactive gas are introduced into the film formation chamber, and a thin film containing sodium atoms is formed on the substrate in the film formation chamber by the action of the reactive gas or the action of the reactive gas and heat.

[0085] In this step, when the source gas and the reactive gas are reacted with each other using heat, the substrate and / or the film formation chamber may be heated. The heating temperature may be in the range of room temperature to 500°C, and a range of 100°C to 400°C is preferred because it facilitates the formation of a high-quality thin film.

[0086] Examples of the reactive gas include oxidizing gases such as oxygen, ozone, nitrogen dioxide, nitrogen monoxide, water vapor, hydrogen peroxide, formic acid, acetic acid, and acetic anhydride, reducing gases such as hydrogen, organic amine compounds such as monoalkylamine, dialkylamine, trialkylamine, and alkylenediamine, and nitriding gases such as hydrazine and ammonia. These reactive gases may be used alone or in combination of two or more. In this step, the reactive gas is preferably an oxidizing gas, and among them, a gas containing oxygen, ozone, or water vapor is more preferred because it reacts well with the thin film-forming raw material of the present invention at low temperatures. Note that when an oxidizing gas is used as the reactive gas, a sodium oxide thin film is formed. Furthermore, in terms of the thickness of the film obtained per cycle being thick and the thin film being able to be produced with good productivity, the reactive gas is preferably a gas containing ozone or water vapor, and more preferably a gas containing water vapor.

[0087] B3. Precursor thin film formation process In the thin film manufacturing method of the present invention, since a high-quality thin film with little residual carbon is likely to be obtained, it is preferable to form the thin film by the ALD method, which includes, between the source gas introduction step and the thin film formation step, a precursor thin film formation step of forming a precursor thin film on the surface of the substrate using the thin film formation source. In a method for forming such a precursor thin film, a sodium compound represented by the general formula (1) in a source gas introduced into a deposition chamber containing a substrate is deposited (adsorbed) on the surface of the substrate, thereby forming a precursor thin film on the substrate surface. At this time, heat may be applied by heating the substrate or the interior of the deposition chamber. The conditions for forming the precursor thin film are not particularly limited, and for example, the reaction temperature (substrate temperature), reaction pressure, deposition rate, etc. can be appropriately determined depending on the type of thin film-forming raw material. The reaction temperature is preferably in the range of 0°C to 400°C, more preferably 100°C to 400°C, since this facilitates the formation of a precursor thin film with a uniform thickness. When the thin film-forming raw material contains precursors other than the sodium compound represented by the general formula (1), the other precursors are also deposited on the substrate surface along with the sodium compound.

[0088] The deposition rate of a thin film (precursor thin film) containing a sodium compound represented by general formula (1) in a raw material gas or a thin film obtained by reacting the raw material gas with a reactive gas can be controlled by the supply conditions (vaporization temperature, vaporization pressure) of the thin film-forming raw material, the reaction temperature, and the reaction pressure. A high deposition rate may deteriorate the properties of the obtained thin film, while a low deposition rate may cause problems in productivity. Therefore, the deposition rate in this step is preferably in the range of 0.005 nm / min to 100 nm / min, and more preferably in the range of 0.01 nm / min to 50 nm / min.

[0089] B4. Other processes B4-1. Exhaust process After the precursor thin film is formed in the precursor thin film forming step, or after the thin film containing sodium atoms is formed in the thin film forming step, it is preferable to have a step of evacuating unreacted reactive gas, raw material gas, and by-product gas from the film formation chamber. In this case, it is ideal that the reactive gas and by-product gas are completely evacuated from the film formation chamber, but complete exhaust is not necessarily required. The degree of vacuum in the evacuation method and the vacuum applied is preferably 0.01 Pa to 300 Pa, more preferably 0.01 Pa to 100 Pa.

[0090] B4-2. Energy application process or catalyst use process The method for producing a thin film of the present invention may also include a step of applying energy such as plasma, light, or voltage, or a step of using a catalyst. The timing of applying the energy or using the catalyst is not particularly limited, and may be, for example, when introducing the source gas in the source gas introduction step, when heating in the precursor thin film formation step or thin film formation step, when evacuating the system in the evacuation step, when introducing the reactive gas in the thin film formation step, or between the steps described above.

[0091] In the thin film manufacturing method of the present invention, when plasma treatment is performed, if the output is too high, the substrate will be severely damaged, so the output is preferably 10W to 1,500W, and more preferably 50W to 600W.

[0092] B4-3. Annealing process Furthermore, the thin film manufacturing method of the present invention may include an annealing step after thin film formation to obtain better electrical properties. In the annealing step, annealing treatment may be performed in an inert atmosphere, an oxidizing atmosphere, or a reducing atmosphere, and a reflow step may be provided if step filling is required. The temperature in this step is preferably in the range of 200°C to 1,000°C, more preferably in the range of 250°C to 500°C, since this facilitates the formation of a thin film with a uniform thickness.

[0093] B5. Film formation cycle The thin film manufacturing method of the present invention may be a method in which the source gas introduction step and the thin film formation step are carried out only once, or a method in which the source gas introduction step and the thin film formation step are carried out two or more times. In the present invention, the thin film formation method is preferably a method in which the source gas introduction step and the thin film formation step are performed two or more times, and more preferably a method (ALD method) in which the source gas introduction step, precursor thin film formation step, evacuation step, thin film formation step, and evacuation step are performed in order, forming a thin film through a series of operations, and this cycle is repeated multiple times until a thin film of the required thickness is obtained, thereby forming a thin film containing sodium atoms having a desired thickness. The thickness of the thin film containing sodium atoms formed can be controlled by the number of cycles. In the thin film production method using the ALD method, thin films of uniform thickness are easily obtained, so the deposition rate of the thin film obtained per cycle is preferably in the range of 0.001 nm / min to 100 nm / min, more preferably in the range of 0.005 nm / min to 50 nm / min.

[0094] C.Thin film Thin films produced using the thin-film-forming material of the present invention can be coated on substrates such as metals, oxide ceramics, nitride ceramics, and glass to form desired types of thin films by appropriately selecting other precursors, reactive gases, and production conditions. The thin films of the present invention can contain other metals in addition to sodium, and can be used for a wide range of applications, including electrolyte membranes and electrode materials for sodium all-solid-state batteries, as well as electro-optical modulators, electrical detectors, optical waveguides, SAW substrates, and piezoelectric transducers. The thickness of the thin films of the present invention may be varied depending on the application. For example, when the thin-film-forming material of the present invention is used in electrolyte membranes for all-solid-state batteries, the electrolyte membrane may have a thickness of approximately 1 nm to 100 μm. [Example]

[0095] The present invention will be described in more detail below using examples, etc. However, the present invention is not limited to the following examples, etc.

[0096] [Production Example 1] Production of sodium compound No. 9 Under an argon gas atmosphere, 9.00 g of sodium amide and 74.4 g of toluene were added to a 200 mL three-necked reaction flask and stirred at room temperature. 28.2 g of 2,4-dimethyl-3-pentanol was added dropwise to the flask to cause a reaction. After the addition was complete, the mixture was stirred at room temperature for approximately 2 hours. The toluene was then distilled off under reduced pressure to obtain a white solid residue. The solid residue was sublimated under a reduced pressure of 90 Pa at a bath temperature of 200°C to obtain a white solid compound. The yield was 68%. Elemental analysis and 1 As a result of H-NMR analysis, the obtained compound was identified as sodium compound No. 9. The analytical results are shown below.

[0097] (1) Elemental analysis (metallic analysis: ICP-AES, organic analysis: CHN) Na: 16.0% by mass (theoretical value: 16.64% by mass), C: 61.5% by mass (theoretical value: 60.84% ​​by mass), H: 10.2% by mass (theoretical value: 10.94% by mass), O: 12.3% by mass (theoretical value: 11.58% by mass)

[0098] (2) 1 H-NMR (solvent: deuterated benzene) (chemical shift: multiplicity: hydrogen number) (0.93~0.95:d:12H)(1.56~1.64:m:2H)(3.1~3.3:m:1H)

[0099] [Production Example 2] Production of sodium compound No. 30 Under an argon gas atmosphere, 0.3 g of sodium amide and 8.77 g of dehydrated toluene were added to a 100 mL three-necked reaction flask and stirred at room temperature. 1.0 g of 2,4,4-trimethyl-2-pentanol was added dropwise to the flask to cause a reaction. After the addition was complete, the mixture was stirred at room temperature for approximately 1 hour. The toluene was then distilled off under reduced pressure to obtain a pale yellow solid. The yield was 97%. Elemental analysis and 1 As a result of H-NMR analysis, the obtained compound was identified as sodium compound No. 30. The analytical results are shown below.

[0100] (1) Elemental analysis (metallic analysis: ICP-AES, organic analysis: CHN) Na: 15.5% by mass (theoretical value: 15.10% by mass), C: 63.8% by mass (theoretical value: 63.13% by mass), H: 11.2% by mass (theoretical value: 11.26% by mass), O: 9.5% by weight (theoretical value: 11.58% by weight)

[0101] (2) 1 H-NMR (solvent: deuterated benzene) (chemical shift: multiplicity: hydrogen number) (1.67:s:2H)(1.49:s:6H)(1.15:s:9H)

[0102] [Production Example 3] Production of sodium compound No. 54 Under an argon gas atmosphere, 2.0 g of sodium amide and 17.35 g of dehydrated toluene were added to a 100 mL three-necked reaction flask and stirred at room temperature. 2.07 g of 2-methyl-1-propoxypropan-2-ol was added dropwise to the flask to cause a reaction. After the addition was complete, the mixture was stirred at room temperature for approximately 1 hour. The toluene was then distilled off under reduced pressure to obtain a pale yellow solid. The yield was 93%. Elemental analysis and 1 As a result of H-NMR analysis, the obtained compound was identified as lithium compound No. 54. The analytical results are shown below.

[0103] (1) Elemental analysis (metallic analysis: ICP-AES, organic analysis: CHN) Na: 15.0% by mass (theoretical value: 14.91% by mass), C: 54.6% by mass (theoretical value: 54.53% by mass), H: 9.9% by mass (theoretical value: 9.81% by mass), O: 20.5% by weight (theoretical value: 20.75% by weight)

[0104] (2) 1 H-NMR (solvent: deuterated benzene) (chemical shift: multiplicity: hydrogen number) (0.9:t:3H)(1.3:s:6H)(1.6~1.7:m:2H)(3.3:s:2H)(3.4:t:2H)

[0105] The sodium compounds obtained in the above Production Examples and sodium tert-butoxide as a comparative compound were evaluated as follows.

[0106] (1)Residue Using TG-DTA, measurements were taken at 760 Torr, with an argon flow rate of 100 mL / min, a heating rate of 10 °C / min, and a scanning temperature range of 30 °C to 600 °C. The mass was measured when the temperature reached 600 °C, and the residue was calculated as the ratio of the mass of the sample after measurement to the mass of the sample before measurement. The smaller the residue, the better the vaporizability and the higher the quality of the thin film that can be produced.

[0107] (2) Temperature (°C) at 50% mass loss in reduced-pressure TG-DTA Measurements were performed using TG-DTA at 10 Torr, an argon flow rate of 50 mL / min, a heating rate of 10 °C / min, and a scanning temperature range of 30 °C to 600 °C. The temperature (°C) at which the test compound's weight was reduced by 50% was evaluated as the "temperature (°C) at which the test compound reduced by 50% by mass in reduced pressure TG-DTA." A lower temperature (°C) at which the test compound reduced by 50% by mass in reduced pressure TG-DTA indicates that vapor can be obtained at a lower temperature. These results are shown in Table 1.

[0108] (3) Temperature (°C) at 50% mass loss in atmospheric pressure TG-DTA Measurements were performed using TG-DTA at 760 Torr, an argon flow rate of 100 mL / min, a heating rate of 10 °C / min, and a scanning temperature range of 30 °C to 600 °C. The temperature (°C) at which the test compound lost 50% by mass was evaluated as the "temperature (°C) at atmospheric pressure TG-DTA 50% mass loss." A lower temperature (°C) at atmospheric pressure TG-DTA 50% mass loss indicates that vapor can be obtained at a lower temperature. These results are shown in Table 1.

[0109] [Table 1]

[0110] As can be seen from Table 1 above, although comparative compound 1, sodium tert-butoxide, produced vapor at a relatively low temperature, the residue was 3.4 wt%. In contrast, sodium compounds Nos. 9, 30, and 54 left little residue, and it was confirmed that sodium compound No. 54 in particular left almost no residue. These results confirmed that the sodium compound represented by general formula (1) is useful as a raw material for thin film formation.

[0111] Example 1 Using the sodium compound No. 54 as a thin-film formation source, a thin film was fabricated on a silicon dioxide substrate using the ALD apparatus shown in Figure 1 under the following conditions. Analysis of the thin-film composition using X-ray photoelectron spectroscopy confirmed that the thin film contained sodium atoms and that the residual carbon content was below the detection limit of 0.1 atom%. Furthermore, measurement of the thin-film thickness using X-ray reflectivity revealed that the thin film formed on the substrate was a smooth film with a thickness of 8 nm, and the film thickness obtained per cycle was approximately 0.016 nm.

[0112] (conditions) Manufacturing method: ALD method Reaction temperature (substrate temperature): 200℃ Reactive gas: water vapor (Process) A series of steps (1) to (4) below constituted one cycle, and 500 cycles were repeated. (1) The raw material gas obtained by vaporizing the thin film forming raw material under the conditions of a raw material container temperature of 60°C and a raw material container internal pressure of 100 Pa is introduced into the film formation chamber, and the sodium compound in the raw material gas is deposited on the substrate surface at a system pressure of 100 Pa for 10 seconds to form a precursor thin film. (2) The source gas containing undeposited sodium compounds is purged with argon for 15 seconds to be exhausted from the system. (3) A reactive gas is introduced into the deposition chamber, and the precursor thin film is reacted with the reactive gas at a system pressure of 100 Pa for 0.2 seconds. (4) Unreacted reactive gases and by-product gases are purged with argon for 60 seconds to evacuate the system.

[0113] Example 2 A thin film was produced on a silicon dioxide substrate under the same conditions as in Example 1, except that sodium compound No. 54 was replaced with sodium compound No. 9. Analysis of the thin film composition using X-ray photoelectron spectroscopy revealed that the thin film contained sodium atoms and had a residual carbon content of 0.1 atom%. Measurement of the thin film thickness using X-ray reflectivity revealed that the thin film formed on the substrate was a smooth film with a thickness of 7 nm, and the film thickness obtained per cycle was approximately 0.014 nm.

[0114] Example 3 A thin film was produced on a silicon dioxide substrate under the same conditions as in Example 1, except that sodium compound No. 54 was replaced with sodium compound No. 30. Analysis of the thin film composition using X-ray photoelectron spectroscopy revealed that the thin film contained sodium atoms and had a residual carbon content of 0.2 atom%. Measurement of the thin film thickness using X-ray reflectivity revealed that the thin film formed on the substrate was a smooth film with a thickness of 8 nm, and the film thickness obtained per cycle was approximately 0.016 nm.

[0115] Comparative Example 1 A thin film was produced on a silicon dioxide substrate under the same conditions as in Example 1, except that comparative compound 1 (sodium tert-butoxide) was used as the thin film-forming raw material. Analysis of the thin film composition using X-ray electron spectroscopy revealed that the thin film contained sodium atoms, but that 2 atom% or more of residual carbon was detected. Furthermore, observation of the thin film condition using a scanning electron microscope revealed that the thin film formed on the substrate was not smooth, making it impossible to measure the film thickness.

[0116] From the above, it was confirmed that when a thin film is produced using a thin film-forming raw material containing a sodium compound with good vapor properties, a smooth, high-quality sodium-containing thin film with little residual carbon can be produced.

Claims

1. A thin film-forming material containing at least one sodium compound represented by the following general formula (1): 【Chemistry 1】 (In the formula, R １ represents a branched alkyl group having 4 to 10 carbon atoms (excluding tert-butyl groups) or a branched alkyl group having 3 to 10 carbon atoms in which one or more hydrogen atoms are substituted with an alkoxy group having 1 to 5 carbon atoms.

2. R in the general formula (1) １ is a secondary alkyl group having 4 to 10 carbon atoms, a tertiary alkyl group having 5 to 10 carbon atoms, or a branched alkyl group having 3 to 10 carbon atoms in which one or more hydrogen atoms are substituted with an alkoxy group having 1 to 5 carbon atoms.

3. 3. The thin film-forming material according to claim 1, wherein the sodium compound is a compound represented by the following general formula (2): 【Chemistry 2】 (In formula (2), R ２ represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, R ３ and R ４ each independently represents an alkyl group having 1 to 5 carbon atoms; R ２ , R ３ and R ４ The total number of carbon atoms in the alkyl groups represented by the formula (I) is 8 or less.

4. A method for producing a thin film, comprising forming a thin film containing sodium atoms using the thin film-forming material according to any one of claims 1 to 3.

5. a source gas introduction step of introducing a source gas obtained by vaporizing the thin film forming source material into a film formation chamber in which a substrate is placed; a thin film formation step of forming a thin film containing sodium atoms on the surface of the substrate by decomposing and / or chemically reacting the sodium compound represented by general formula (1) contained in the source gas; The method for producing a thin film according to claim 4 , comprising:

6. a precursor thin film forming step of depositing a compound represented by general formula (1) contained in the source gas on the surface of the substrate to form a precursor thin film between the source gas introducing step and the thin film forming step, 6. The method for producing a thin film according to claim 5, wherein the thin film forming step is a step of forming a thin film containing sodium atoms on the surface of the substrate by reacting the precursor thin film with a reactive gas.

7. 7. The method for producing a thin film according to claim 6, wherein the reactive gas is an oxidizing gas, and the thin film is sodium oxide.

8. 8. The method for producing a thin film according to claim 7, wherein the oxidizing gas is a gas containing oxygen, ozone, or water vapor.

9. 9. The method for producing a thin film according to claim 6, wherein the thin film forming step comprises reacting the precursor thin film with the reactive gas at a temperature in the range of 100°C to 400°C.

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